One Thing Each Day by Tony Lembke

The circumference of a circle is slightly more than three times as long as its diameter. The exact ratio is called π.

π – the ratio of the circumference of a circle to its diameter – is a mathematician’s favourite number. It is both irrational and transcendental – it will continue infinitely without repetition or pattern.

As you know, π is just over 3, and is often approximated as 22 divided by 7, or 22/7 (so in Australia we should celebrate Pi day on 22nd July!)

To be more accurate, π is 3.14159

(Last year was a very special Pi day – 3.14.15 . This year – 3.14.16 – might be said to be rounded Pi day)

To be even more accurate, Pi has been calculated to over one trillion digits beyond its decimal point. What larks!

The ratio of a circle’s circumference to its diameter was known to be about 3 since ancient times (as mentioned in the Bible). Archimedes in ancient Greece proved it to be 22/7.

However, the use of the symbol π (for perimeter) to represent this ratio was not used until 1706, and was popularised by the prolific Swiss mathematician Euler later that century.

Speaking of Euler, the peak of our mathematical education at school was the day Mr Garrity showed us the proof of the world’s most beautiful equation. He was bursting with delight as he worked through the steps that reveal the relationship between the 5 most important constants in all of mathematics. Euler’s Identity – “more beautiful than a Shakespeare sonnet”.

π has featured in the Simpsons – so much so that mathematician Simon Singh has written a book on the subject.